TREASURY DEPARTMENT 
UNITED STATES PUBLIC HEALTH SERVICE 

HUGH S. GUMMING, Surgeon General 



STUDIES OF RECONSTRUCTED 
MILK 



BY 

ALBERT F. STEVENSON 

Sanitary Engineer 

GEORGE C. PECK 
Scientific Assistant 

AND 

C. P. RHYNUS 

Assistant Sanitary Engineer 
United States Public Health Service 



-(;-z;^'l1 



REPRINT No. 608 

FROM THE 

PUBLIC HEALTH REPORTS 

August 27, 1920 
(Pages 2011-2045) 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1920 






ADDITIONAL COPIES 

OF THIS PUBLICATION MAY BE PROCURED FROM 

THE SUPERINTF.NDENT OF DOCUMENTS 

GOVERNMENT PRINTING OFFICE 

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DEC 11 1920 



t4 



STUDIES OF RECONSTRUCTED MILK.* 

By Albert F. Stevenson, Sanitary Engineer; George C. Peck, Scientific Assistant; and C. P. 
Rhynus, Assistant Sanitary Engineer, United States Public Health Service. 

FOREWORD. 

By Earle B. Phelps, Consultant, United States Public Health Service. 

Pure milk contains a variety of substances, which, for convenience 
in analysis and reference, are conventionally divided into three groups : 
Fats, solids not fat, and water. The proportions of these three groups 
in the mixture vary with the breed of cattle, the feed, the season, and 
other variable conditions, but it will be sufficiently accurate for the 
present purposes and for illustration to say that normal milk contains 
3J per cent fats, 9 per cent solids not fat, and 87J per cent water. 

At a time when, in the interests of food conservation, the possibili- 
ties of desiccated foodstuffs are being developed and their economic 
advantages exploited, it is unnecessary to dwell at length upon the 
purely economic benefits which would accrue were it possible to deal 
with the milk supply of the country and, especially, with its problems 
of storage and transportation, upon a water-free basis. 

Desiccation in general has two principal advantages: It reduces the 
weight of the commodity, thereby simplifying the problem of distri- 
bution ; and it improves the handling and keeping qualities of perish- 
able foods by doing away with the watery environment necessary for 
microbial activity. These advantages make it possible to distribute 
foodstuffs over wide geographical areas and thus to provide markets 
for those regions in which production is deficient or lacking. They 
also make possible a seasonal distribution or leveling, whereby the 
commodity may be carried over from a season of excessive production 
into a season of nonproduction. 

To these manifest advantages, which are common in the entire field 
of desiccated food, there is added, in the case of milk supplies, a third 
of equal if not greater importance. This has reference to the sani- 
tary aspects of the milk problem, which have so occupied the atten- 
tion of public-health workers in recent years. Milk provides so favor- 
able a medium for the growth and multiplication not only of normal 
and relatively harmless bacteria but also of the specific organisms of 
disease that the entire development of this important food supply, 

'■ Made under the supervision of Earle B. Phelps, Consultant, United States Public Health Service. 
Reprint from the Public Health Reports, vol. 35, No. 35, Aug. 27, 1920, pp. 20U-2045. 

3 



4 STUDIES OF RECONSTRUCTED MILK. 

especially as it relates to large cities, has been impeded and very 
seriously complicated by the necessary public-health restrictions. The 
storage and shipping of milk must be done at low temperature and 
can not extend beyond a few days at most, and pasteurization has 
come to be a recognized essential feature in the handling of a city 
milk supply. 

If, now, it were possible to desiccate the product in its fresh con- 
dition by a process which would greatly reduce the existing bacterial 
life and prevent the further multiplication of the surviving organisms, 
the limitations referred to would in large measure disappear. 

The actual realization of these conditions and the possibility of 
supplying to a community a milk reconstructed from its previously 
desiccated components and water, have been made possible by a 
series of steps, the commercial development of which has been taking 
place for many years. These are the mechanical separation of the 
fats in the form of cream from the skimmed milk^ and modern proc- 
esses of butter making; the development of processes, first, of 
skunmed milk evaporation, and, finally, of complete desiccation 
to a powder containing, in readily soluble form, all the milk solids 
except the fats; the development of mechanical means of emulsi- 
fying butter fat in water or skimmed milk solution, thus reconstruct- 
ing the cream; and, finally, the conception of reconstructing a whole 
milk, by emulsifying butter fat into a solution of milk solids of proper 
strength. 

This paper is a report of what is believed to be the first experiment 
upon a commercial scale with reconstructed milk. While the advan- 
tages of the plan, under many conditions, are so obvious that the 
idea had frequently been discussed, there were at the outset of this 
investigation certain difficulties to be overcome. In order to prevent 
fraud and protect health, it has been necessary for the States and 
the Federal Government to enact food laws which prohibit, in large 
measure, modification of natural food products. This raised the 
question of the propriety of the proposed procedure, which admit- 
tedly makes fraud, in the terms of the pure food law, easy and its 
detection difficult. 

The particular situation which has been created by the possibilities 
of reconstructed milk is without precedent, and, as it deals with one 
of the most fundamental of the human foods, a most conservative 
attitude upon the part of the officials charged with the enforcement 
of the pure food laws has very properly been maintained. In view, 
however, of the tremendous advantages which are foreseen in the 
development of this field, it is believed that the problem must be 
handled entirely upon its own merits, and with the utmost frankness. 
There can be no question of the impropriety of handling reconstructed 



STUDIES OF RECONSTRUCTED MILK. 6 

milk, except under its own label and with complete information as 
to its source and method of preparation. If it can be shown, however, 
that reconstructed milk can be marketed in a community under 
cleaner and safer conditions and at less cost than can ordinary milk, 
the consumer is entitled to these advantages just as he is also entitled 
to know exactly what he is purchasing, and, if he prefers to use fresh 
cows' milk, to be assured that he receives that for which he asks and 
pays. 

A second possibility which has prevented more active development 
of reconstructed milk has been the fear that the public might be 
slow to appreciate its advantages and reluctant to give up a part 
of the dietary so well established as milk in favor of what must 
appear to be a sort of manufactured product. While this argument 
will carry no weight whatever among physicians, dietitians, and 
others competent to look into the subject with sufficient thorough- 
ness, it is a matter to be reckoned with most thoughtfully by one 
who would undertake the commercial development of a market for 
reconstructed milk. 

In the situation which arose at the new Government city of Nitro, 
W. Va., both of these objections lost most of their force. A city 
to house some 25,000 people was being built overnight, and w^as 
without any visible milk supply, nor did it seem probable that a 
sufficient supply of safe milk could be obtained. The health admin- 
istration of this city was to be in charge of the United States Public 
Health Service, so that there could be no question of conflict with 
traditional health regulations. The conditions made it unnecessary 
to fear competition with normal milk, so that it was practically 
assured in the beginning that, if the milk was satisfactory, a market 
would be secured. Under these favorable conditions a plan which 
had been gradually maturing was put into effect, and the present 
paper is a report of the results obtained. Unfortunately for this 
particular purpose, the experiment had to be discontuiued before 
the complete data that were hoped for had been gathered. It is 
believed, however, that the results obtained are of so great impor- 
tance that the outcome of this first commercial demonstration of 
the possibilities of reconstructed milk should be recorded. 

Mr. Stevenson designed the plant and prepared the specifications 
for the mechanical equipment and has been wholly responsible for 
the planning and execution of the experimental work. He has been 
ably assisted throughout by Mr. Peck who was in resident charge 
during the construction period, and who, in the capacity of super- 
intendent, was directly responsible for the operation of the station. 

Mr. C. P. Rhynus made the bacteriological studies, and Mr. Leslie Z. 
Peck served as assistant superintendent. 



6 STUDIES OF RECONSTRUCTED MILK. 

I. THE MANUFACTURE AND HANDLING OF RECONSTRUCTED MILK AT 

NITRO, W. VA. 

By Albert F. Stevenson, Sanitary Engineer, and George C. Peck, Scientific Assistant, United States 

Public Health Service. 

Introduction. 

Nitro, W. Va., is located on the Kanawha Eiver, about 13 miles 
from Charleston. It was built by the United States Government to 
house the laborers and mechanics employed in building the United 
States Explosives Plant C and later to house persons permanently 
employed in the smokeless-powder plant. Accommodations were 
made for about 25,000 inhabitants. The several institutions and 
industries necessary to form a well-organized conmiunity, such as 
schools, churches, hospitals, department stores, restaurants, water 
supply, sewerage, abundant food supply, etc., were provided. In 
short, a modern city was constructed on the land surrounding the 
explosives plant. 

The construction of this city and the organization of the various 
necessary secondary industries was accompanied by many difficulties 
which were increased by war-time conditions. The gathering together 
of sufficient food of satisfactory quality proved to be one of the 
serious difficulties, and radical departures from current practice 
were made in order to overcome them. One of the most interesting 
and instructive divergencies was made in securing a sufficient 
quantity of fluid milk to satisfy the demand. The present article 
deals with this part of the work. 

Available Normal Source of Milk. 

Very little milk is produced in West Virginia in the vicinity of 
Nitro. The region is mountainous and little if any natural pasturage 
is available. In fact, previous to the building of the various Govern- 
ment industries located in this section, hardly enough local milk was 
available to supply the normal Charleston market. Up to the time 
Nitro was conceived, little attempt was made to increase the supply. 
Some milk was shipped in from the dairy section of Ohio, but with 
the advent of war, the scarcity of milk and the congestion of railroad 
traffic made this source undependable. The United States Public 
Health Service was called on to suggest some method of procuring a 
milk supply for Nitro. 

Reconstructed Milk Products. 

For pome time it has been known that a liquid closely resembling 
milk and cream could be made by emulsifying butter fat obtamed 
from unsalted butter in a solution of skimmed milk powder or diluted 
evaporated skimmed milk. This procedure has been very widely 



STUDIES OF RECONSTRUCTED MILK. 7 

used by the ice-cream industry and has been sanctioned for this piu"- 
pose by the -pure-food officials. This liquid has also been made in 
small quantities at some Army field hospitals, and on several of the 
battleships to furnish a supply to the officers' mess. It has been 
made at various dairy and milk shows as a means of advertising 
milk powders. 

The manufacture of reconstructed products on a small scale led to 
the assumption that a fairly large-scale plant could be successfuUy 
operated and the milk supply of a city the size of Nitro manufac- 
tured. After conferring with officials of the department of health 
and sanitation and the commissary department at Nitro, it was 
decided to recommend the building and equipping of a plant of suffi- 
cient capacity to supply the entire city with reconstructed milk and 
cream. It was certain that milk could be made which would be 
satisfactory if consumed within a few hours of the time of manufac- 
ture; but little, if anything, was known about the cost of manu- 
facture, the method of handling, and the keeping qualities of the 
products. 

In order to make a thorough investigation of the subject and at 
the same time supply Nitro with milk, the Public Health Service 
undertook to design the plant and superintend its operation as long 
as the process was in the experimental stage. An equipment was de- 
signed which, it was estimated, would handle 2,000 gallons of bottled 
milk in an eight-hour day, and which capacity could be increased to 
3,000 gallons per day by the addition of another pasteurizing and 
emulsifying unit. Milk and cream could be handled in either bulk 
or bottled form, although equipment of sufficient size to bottle all 
the output was provided. It was expected that all milk sold, except 
that used for cooking, would be served in bottles. 

Description of Building. 

The "milk plant" was located in the south end of the reserva- 
tion in a one-story frame building 150 feet long and 51 feet wide. 
This same building also housed a small cold-storage warehouse used 
by the commissary department for the storage of perishable foods. 
The space allotted to the manufacture of reconstructed milk was 123 
feet long and 51 feet wide. This space was somewhat excessive, but 
on account of the experimental character of the work, extra room 
was provided. The general plan of the building is shown in Figures 
1 and 2, and a sectional elevation in Figure 3. The building was 
divided into eight rooms: A milk manufacturing room; a room for 
the washing of containers; cold-storage space for milk and butter; 
a dressing room; a storage room for milk powder; an office; and a 
room for the refrigerating machinery. 



STUDIES OF RECONSTRUCTED MILK. 




4 1 , >« < !• <t j; 



STUDIES OF RECONSTRUCTED MILK. 



9 



The milk room was 40 feet long and 50 feet wide. In the south- 
west corner was located a balcony, elevated 8^ feet from the main 
floor. This balcony was 27 feet long and 17 feet mde. An emer- 
gency exit from this room to the west platform was provided, but it 
was kept locked while the plant was in operation. 

The washing room was 35 feet long and 50 feet wide. In the south- 
west corner of this room was located a platform 8 by 18 feet, raised 
about 6 inches from the main floor. It could be entered from both 
outside platforms. 

Reconstructed Milk Plant 

N I T R , W. VA . . ^^ SrsAM d Hat£R Connect toN 
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"TESTER" 



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BUTTER 
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Balcony Plan. 

Fig. 2. 



I 



The refrigerator was 30 feet long by 23 feet wide. It could be 
entered from the milk-manufacturing room through a single refrig- 
erator door, or from the east platform through two doors and a 
vestibule. The room was large enough to store one day's output of 
the plant, together with a carload of ice. 

The butter-storage room was 30 feet long by 9 feet wide. It could 
be entered only from the milk-storage room. This room was large 
enough to store two carloads of butter. Both of the cold-storage 
rooms were insulated with rock cork and were plastered inside with 
cement plaster. They had an available head room of 6 feet 7 inches. 
12325°— 20 2 



10 



STUDIES OF EECOISrSTRUCTED MILK. 




Public Health Reports. Reprint 608. 




Fig. 4.— Manufacturing and bottling room, Reconstructed Milk Plant, Nitro, W. Va. 




Fig. 5.— Mixing vats and emulsors. Reconstructed Milk Plant, Nitro, W. Va. 



STUDIES OF RECONSTRUCTED MILK. 11 

The dressing room was approximately 15 feet square, and could 
be entered from the wash room. It contained hand bowls and toilets 
and lockers for clothing. 

The room for the storage of milk powder, which was 20 feet by 16 
feet, was of sufficient size to store 100 barrels. 

The office was 16 feet square and contained a desk, chairs, a table, 
and a telephone. The office could be entered from the outside and 
also from the washing room. This outside entrance was the only 
entrance used by those not employed at the plant. 

The room containing the refrigerating machinery was 30 feet long 
by 15^ feet wide. The floor of this room v;as at the ground elevation 
and could be reached by a short stairway leading from the milk room. 

The main floor of the building was made of heavily reinforced con- 
crete, and was elevated about 5 feet above the ground level. It 
extended 8 feet beyond the walls of the building on either side, 
forming concrete receiving and sliipping platforms. All rooms, with 
the exception of the office and the milk-powder storage room, were 
supplied with floor drains connected to the sewer. 

The inside finish of the rooms consisted of a 5-foot wainscotins: of 
cement plaster over metal lathing extending around the base of the 
walls. Above this wainscoting the walls were finished with matched 
siding. Plaster board was nailed to the rafters to within 10 feet of 
the peak of the roof. At this point the plaster boarding was carried 
across to the opposite rafters, forming a horizontal ceiling with an 
air chamber above. The wainscoting was tinted a dark blue-gray, 
and the walls and ceiling were painted with white enamel over flat 
white. The inside of the refrigerators was painted with white enamel 
over flat white. This color scheme proved to be practical and very 
pleasing in appearance. 

The milk room and wash room were ventilated by means of five 
ventilators operated by natural draft. These ventilators extended 
through the roof into the air chamber, which, in turn, was provided 
with openings located directly under the ventilators. 

EQUIPMENT. 

On account of the experimental nature of the plant, the equipment 
was purchased with the idea of acquiring units which could be re- 
arranged at wfll, until a satisfactory layout was obtained. The milk- 
handling machinery, located in the milk room, consisted of a butter- 
milk machine of 300 gallons capacity; a milk pump; two 300 gaUon 
ice-cream batch mixers; two centrifugal emulsors of 200 gallons ca- 
pacity each, belt-driven from 2-horsepower motors; one tubular milk 
cooler of 5,000 pounds per hour capacity, composed of two sections, 
one for water and one for brine; an antifoam tank; a I'otary bottle 
filler and capper; scales and tank for weighing water, and scales for 
weighing butter; a porcelain topped table for cutting butter; and a 



12 STUDIES OF RECONSTRUCTED MILK. 

Babcock tester. The locations of these machines are given in Figures 
1 and 2. All of this machinery, except the mixing and pasteurizing 
vats, emulsors, butter scales, and butter-cutting table, was located 
on the main floor. These machines were on the balcony, as shown 
in Figures 2, 3, and 4. 

As it was necessary to start the construction of the building before 
all of the machinery had been selected, it was not possible to deter- 
mine the headroom necessary to insure a gravity system from the 
mixing vats to the bottle filler. It was found necessary, therefore, 
to elevate the mixing vats about 2 feet above the floor of the bal- 
cony. They were supported on a stand made of 2-inch pipe. This 
arrangement made speed in operation difficult and should be avoided. 
Figure 3 gives the elevation necessary for a gravity system. 

All machines were connected with 1^-inch sanitary milk piping, 
and the valves and fittings were of the easily cleanable sanitary type. 
A no-foam can filler was installed between the antifoam tank and 
the bottle filler. All machines were driven by individual motors, 
thus doing away with the inconvenience of overhead shafting. The 
plant as designed was not equipped to manufacture ice cream, 
but when operations were started it was found necessary to manu- 
facture a small amount of this product each day. A 60-quart con- 
tinuous brine freezer was purchased but was never operated. In 
order to tide over until this machine was available for use, two of 
the old type can freezers were set up and operated. They were 
motor driven and were located under the balcony against the wall 
of the machinery room. 

Bottles were washed with an automatic jet washer, having a ca- 
pacity of approximately 4,000 bottles an hour. The pumps of this 
machine were operated by a direct-connected 10-horsepower motor. 
Tills washer was located in the center of the washing room and was 
oriented so that the bottles coming from the machine could be 
trucked directly into the milk room and stored. A small galvanized- 
iron tank used for the washing of cans, which process was carried 
out by hand, together with a rinser and steamer, was located against 
the south wall of the washing room, as shown in Figure 1. A small 
brush washer, on which extremely dirty bottles could be scrubbed, 
was located on the north wall of the washing room. A two-effect 
water still with a capacity of 350 gallons per hour was located on the 
raised platform in the southwest corner of the washing room. The 
effluent pipe from this stiU projected through the waU into the milk 
room and discharged into a tin-lined distiUed-water storage tank of 
1,000 gallons capacity. This storage tank was connected by tinned- 
covered piping to the suction end of the milk pump. At this point 
a three-way valve was located, so that fluid could be drawn from 
either the distilled water tank or the buttermilk machine as desired. 



STUDIES OF RECONSTRUCTED MILK. 13 

The discharge from this pump was also arranged so that the effluent 
could be sent dither into a weighing can mounted on a small plat- 
form near the skimmed-milk vat, or to the mixing vats on the 
balcony. 

A small field laboratory for determining the bacteriological content 
of milk and milk products as weJl as the acidity and fat in milk, was 
located in the dressing-room. This laboratory will be described in 
the section on the analytical study of reconstructed milk products. 
A Babcock centrifuge was located on a stand on the balcony in the 
milk room, where frequent tests of the finished product could be 
conveniently made. 

The refrigeration used for both the reconstructed milk plant and 
the cold-storage department of the commissary was furnished by a 
15-ton refrigerating machine. The ammonia compressor was driven 
by a 30-horsepower motor. All of the refrigerator rooms were cooled 
directly by the expansion of the compressed ammonia. Brine, 
cooled by the expansion of ammonia, was used for cooling the recon- 
structed milk. The brme was circulated by a steam-di'iven brine 
pump. 

WATER SUPPLY. 

The water used throughout the plant was obtained from the regular 
Nitro supply, which had previously been filtered and chlorinated. 
This water, brought into the building through a 3-inch main, was 
used only for cleaning and cooling purposes. 

STEAM SUPPLY 

The steam used in the plant was generated in a central power 
plant located about 600 feet from the milk plant. It was brought 
to the plant by a 4-inch steam main. 

Plant Operation. 

RECONSTRUCTED MILK PRODUCTS DEFINED. 

As has been stated, reconstructed milk products are products made 
by the emulsification of butter fat m normal or reconstructed skimmod 
milk. Reconstructed skimmed milk may be made either by diluting 
unsweetened condensed or evaporated skimmed milk with distilled 
water or by dissolving dried skimmed milk powder in distilled water. 
The percentage of fat and solids not fat may be adjusted to suit the 
use which is to be made of the product, provided these percentages 
are plainly stated on the package. In the work described below 
skimmed milk powder was used exclusively as a source of solids not 
fat, and a high grade of unsalted butter as a source of butter fat. 
Reconstructed milk, reconstructed cream, ice-cream, and fermented 
milk products, such as cultured buttermilk and cottage cheese, were 
all manufactured. 



14 STUDIES OF RECONSTRUCTED MILK. 

INGREDIENTS. 

In the reconstruction of milk it should be borne in mind that no 
matter foreign to normal cow's milk should be added to the product. 
It is necessary, therefore, to use only the purest water, and the 
highest grade of dried skimmed milk and butter. The finished 
product can grade no higher than the ingredients used. The extreme 
importance of this point justifies a detailed discussion of each ingre- 
dient. 

Water. — Nothing but the very purest of water, from both a chem- 
ical and bacteriological standpoint, should be used in the reconstruc- 
tion of milk. Assuming that a normal water supply is available, 
which is free from all harmful bacteria, this water may contain mineral 
salts which might possibly be harmful to the weak digestion of an 
infant. For example, the hard waters of the Middle West and those 
containing a high percentage of sulphate could very easily cause 
intestinal disturbances in the young. Also, from the manufacturing 
standpomt, these salts would very probably have a deleterious effect 
on the physical state of the emulsion. It is very probable that, in 
some districts, a very pure water, free from mineral constituents and 
free from all pollution might possibly be obtained, but this condition 
is so rare that only distilled water should be considered as a general 
source. 

From a bacterial standpoint, water that is not absolutely free from 
pollution would be much more dangerous when used in milk than 
when used as water, for the growth of the harmful bacteria could 
easily take place in the excellent food medium which is furnished, and 
a very small number of pathogenic organisms gives rise to a number 
sufficient to be harmlul. As the best of our filtered supplies may 
contain a small number of disease-producing organisms, practically 
all waters except those which have been freshly distilled are elimi- 
nated. It is, therefore, strongly recommended that no reconstructed 
milk products be manufactured without using water which is free 
from dissolved salts and pathogenic bacteria. 

From a commercial standpoint it is highly important that the 
water used in the manufacture of milk products should be free from 
objectionable tastes, odors, sediment, and color. Even the char- 
acteristic flavor of poorly made distilled water may be easily dis- 
tin :uished after the milk powder and butter have been added. This 
flavor ;dso increases with the a<i:e of the milk and is decidedly objec- 
tionable in a product 24 to 48 hours old. In selecting a still for the 
manufacture of distilled water great importance should be placed on 
the ability of this still to produce a tasteless and odorless product. 

SHmmed milJc powder. — The skimmed milk powders available on 
the market to-day may be divided into three classes : Those made by 
drying on rolls at atmospheric pressure and a relatively high tempera- 



STUDIES OF RECONSTRUCTED MILK. 15 

ture; those made by drying under reduced pressure and a corre- 
spondingly lower temperature; and those made by drying a finely 
atomized milk in a current of hot, dry air. The manufacturers of 
powder made by the various processes claim advantages over ]>owders 
made by other processes, and the purchaser must decide on the 
product best suited to his needs. 

In the manufacture of reconstructed milk, the follow^ing points 
are of extreme importance in the selection of a skimmed-milk powder: 

The powder should be wholly and easily soluble in water and when 
reconstructed should give a solution with the characteristic flavor of 
normal skimmed milk. 

The various constituents, such as the sugar, proteins, and mineral 
salts, should not have been altered during drying, and upon recon- 
struction should appear in as near the original state as possi])le. A 
solution of the powder should have the powder to hold an emulsion 
of butter fat similar to that found in normal milk. 

As the reconstructed milk must meet all the legal requirements of 
normal market milk, the original milk used for drying must be pro- 
duced in a cleanly fashion, and must meet all requirements of the 
local health department of the district where the reconstructed milk 
is to be sold. The process of drying should also be conducted in a 
cleanly manner, and rules prescribed for the handling of normal milk 
should be enforced in the manufacture of the skimmed-milk powder. 
It is needless to say that this powder should contain only and all the 
ingredients occurring in normal skimmed milk, with the exception of 
the water. Skimmed-milk powder is deliquescent and absorbs 
moisture rapidly. If the moisture content is high, the powder will 
lump in the containers and be unfit for use. It should therefore be 
stored in moisture-proof containers and should be sold with a 
guaranteed maximum moisture content. 

Butter fat. — Sw^eet or unsalted butter is used as a source of butter 
fat. A good quality of sweet butter is almost as difficult to obtain 
as a good quality of skimmed milk powder or water. It should have 
good flavor, be free from pathogenic organisms, and be manu- 
factured in such a manner that objectionable flavors and odors will 
not be produced in it during storage. It should never be artificially 
colo»"ed, and manufacturers should guarantee the butter-fat content. 
The butter should be shipped in proper containers, and every con- 
tainer should be scored by the purchaser before it is accepted. 
Butter should be stored at a temperature sufficiently low to prevent 
the production of disagreeable flavors and odors and should be taken 
out of storage only as needed. 

Commercial Manufacture of Reconstructed Milk. 

RECONSTRUCTION OF SKIMMED MILK. 

If the skimmed milk powder to be used has been selected with 
proper care the process of dissolving it is not a difficult one. At 
KiUo a val buUermilk machine of ordinary design was used for this 



16 STUDIES OF RECONSTRUCTED MILK. 

purpose. This machine was of 300 gallons capacity and was equipped 
wdth a revolving heating coil to which blades were attached, serving 
simultaneously as agitator and heater. In selecting a vat, care should 
be taken to obtain one with a cylindrical bottom, and sides which are 
tangential to the surface of the cylinder. There should be no corners 
in which the undissolved powder may be pocketed. The necessary 
amount of distilled water should be placed in the vat and a weighed 
amount of skimmed milk powder added. The powder may be dumped 
in directly from the barrel, if care is taken to prevent foreign matter 
from falling from the sides of the barrel during the process. It was 
found that better results were obtained when the powder was removed 
from the barrel with a large sugar scoop. The coil agitator should be 
in operation while the powder is being added. The temperature of 
the water during the period of solution of the powder should be 
between 70° and 80° F. 

Adding butter, and pasteurization.— After the complete solution of 
the powder had taken place, the skimmed milk was pumped to one of 
the mixing vats on the balcony. Here the necessary amount of 
butter, which had previously been cut into 4-inch cubes on the 
porcelain topped table provided for the purpose, was added, and the 
mixture brought to a temperature of 146° F., and held there for 30 
minutes. It was found that by the time the temperature had reached 
146° F. all the butter had melted. The holding time for the pasteuri- 
zation of the skimmed-milk-butter mixture may therefore begin 
when the correct temperature is reached. It is necessary, however, 
to cut the butter into 4-inch cubes or less if this procedure is to be 
followed. 

Emulsifying the hutterfat. — After the mixture had been pasteurized, 
and while it was at the pasteurizing temperature, it was passed 
through the centrifugal emulsors. 

Emulsification is brought about by the forcing of the mixture 
of butter and skimmed irdlk through an extremely narrow opening, 
using centrifugal force generated by revolving the bowl of the emulsor 
at a speed of approximately 15,000 revolutions per minute. 

Cooling. — From the emulsors the hot reconstructed milk was con- 
ducted to the upper trough of the cooler through sections of 1^-inch 
sanitary milk pipe to which had been attached small conductor heads. 
The milk from the emulsors contained a great deal of foam, and 
difficulty was experienced in transmitting this foaming product to 
the cooler. A large bank of foam collected where the milk entered the 
conductor head and also in the upper trough of the cooler. This 
necessitated the providing of ample capacity at both of these points 
to prevent the foam from accumulating and running over the edge 
of the conductor head and trough. For this reason it is felt that the 
use of an external cooler should be avoided in this process. The use 



STUDIES OF RECONSTRUCTED MILK. 



17 



of an external tubular cooler would eliminate to a great extent this 
waste and .inconvenience. By inserting an antifoam tank, as 
described below, between the emulsor and the cooler, much of this 
trouble might be eliminated. This arrangement was not tried at 
Nitro, however. 

A proper regulation of the temperature of the milk as it leaves the 
cooler is an important point in the process of manufacture. As with 
ordinary milk, freezing throws the butterfat out of emulsion to a 
greater or less degreee. The flow of brine should therefore be regu- 
lated so that a minimum amount of milk freezes to the cooler. All 
milk which does so freeze should be re-emulsified before bottling. 
Satisfactory results can be ob- 

' ^' — .f2f^M Level ^'V* 



.Milk 
/^Ourter 



Milk Level 



16". 



Milk 

iENTERS; 
- 1 ^ 



Fig. G. — Section of aniifoam tank used at the Recon- 
structed Milk Plant, Nitro, W. Va 



tained if the milk leaves the 
cooler at a temperature of from 
40° to 50° F. 

Foam removal. — As has been 
stated, the reconstructed milk 
as it leaves the emulsor con- 
tains a great deal of suspended 
air. This air is in such a finely 
divided state that it is elim- 
inated slowly. Bottles filled 
with the milk directly from 
the cooler show, on two hours 
standing, an air space between 
the cap and the surface of the 
milk varying from 1 inch to 3 
inches in height. In order to 
eliminate this foam an antifoam 
tank was inserted between the cooler and the can and bottle fillers. 
This foam tank is simply a detention tank, from the bottom of 
which the milk is drawn. A sketch of it is shown in Figure 6. With 
the emulsors running at full capacity (approximately 400 gallons per 
hour) this tank gave a detention time of approximately Z\ minutes. 
This arrangement eliminated practical^ all tlie foam from the 
milk. 

Filling containers. — From the foam tank the milk passed into a 
rotary bottle filler, A "no foam" can filler was inserted between 
the antifoam tank and the bottler. At this point all the cans were 
filled. The bottle filler was driven by a direct-connected motor and 
had a capacity sufficient to handle the effluent from the emulsors. 
This type of filler and capper has a decided advantage over a case 
filler in that all bottles have to be handled twice and therefore get 
two inspections. When using the case filler there is a great tendency 
to slight the bottle inspection, and many damaged bottles which 
12325°— 20 3 



18 



STUDIES OF RECONSTRUCTED MILK. 



should not be used are filled and put into circulation. The bottles 
used were of the ordinary glass, common-sense type, capped with 
paper caps. As is customary, the caps bore the package label. 

Storage. — Immediately after the containers were tilled they were 
trucked into the cold-storage room, where they remained until 
delivered. The temperature of this room was approximately 33° F. 

Labeling. — ^Regulations pertaining to all foodstuffs should be ap- 
plied to reconstructed milk products. These products should be 
sold only for what they are and only when the packages are properly 
labeled. According to the present law, a milk made from skimmed 
milk powder, water, and butter is not "milk," and should not be 
sold as such. The law distinctly states that milk is the normal 
fluid secreted by the mammary glands of the cow, and a product 
which has been reconstructed certainly can not be classed as "milk." 

In choosing a name for this product various titles have been con- 
sidered. From the list has been chosen the term "reconstructed 
milk." It is felt that this is fully descriptive and leaves no reason 




Fig. 7. — Bottle caps used at the Reconstructed Milk Plant, Nitro, W. Va. 

for doubt as to the product. The word "reconstructed" may pos- 
sibly arouse some sense of fear in the minds of the unenlightened con- 
sumer, for it may signify to him a product which has been at some 
time in an unsatisfactoiy condition and later renovated. Various 
other names which have been suggested are "remade," "emulsified," 
"reconstituted," "recombined," and "rehydrated." Any of these 
terms may be used, subject to the approval of the officials who are 
intrusted with the enforcement of the pure-food laws. 

In labeling any of these manufactured products the word "recon- 
structed," or any other similar word which may be used, should be 
given as much prominence as the word "milk." The label should 
also set forth the percentage of butter fat and the percentage of milk 
solids not fat which the product contains. Figure 7 shows samples of 
the various caps used at Nitro. The reconstructed milk manufac- 
tured there contained 9 per cent milk solids not fat and 3h per cent 
butter fat. The cream contained 25 per cent butter fat. A form 
of fermented milk similar to buttermilk was manufactured and styled 



STUDIES OF RECONSTRUCTED MILK. 19 

"Nitrolac." It was not considered proper to label this milk butter- 
milk, for the term "buttermilk" has a distinct meaning. It is a 
product of the churning of milk or cream and the name should be 
used for no other product. The fermented milk used at Nitro was 
simply a cultured milk of a low percentage butter fat. 

Washing containers. — ^All containers were washed in the room pro- 
vided for that purpose. The bottles were inverted and washed in 
the cases. The washer used consisted of a series of tanks from which 
water or alkali solutions were pumped with considerable pressure 
through a series of jets. The cases were intermittently advanced by 
a mechanical device and the jets so arranged that during the resting 
period a powerful stream of water or chemical solution was injected 
into each bottle while a number of streams were forced against the 
outside and inside of the case. The temperature of the first rinse 
water was approximately 110° F., a temperature sufficient to warm 
the cold bottle without danger of breaking it. The temperatures 
of the subsequent washing and rinsing solutions were so regulated 
that the final temperature of the bottle was approximately that of 
boiling water. Before leaving the machine each bottle was subjected 
to a jet of live steam which acted as the final sterilizing agent. 

All cans and metal containers were washed by hand in a galvanized 
iron tub provided for the purpose. After a thorough brushing with 
an alkali sc^lution, the can and cover were inverted over a can rinser 
and sterilizer where they received a hot-water rinse and a thorough 
steaming. 

Cleaning milk-handling machinery. — At the end of each day's run 
all milk-handling machinery and piping were completely disassembled, 
rinsed with warm water, scrubbed with a brush and hot alkali solu- 
tion, rinsed with hot water, and then sterilized by blowing live steam 
into or through them for a considerable time. The machinery was 
then partially assembled. In the morning before operations com- 
menced, the machinery was completely assembled and connected at 
various points to the steam line. Steam was blown through the 
assembled machinery for approximately 20 minutes. This produced 
a satisfactory sterilization. 

The most difficult piece of machinery to sterilize was the tubular 
cooler. This is the general experience where this type of cooler is 
used. At the end of the run the tubes are full of water or brine, and 
the ordinary methods of steaming are not sufficient to heat the whole 
mass up to the sterilizing point. Satisfactory sterilization may be 
accomplished by emptying the tubes and either blowing steam, under 
pressure, through them, or by inserting a steam hose between the 
covers and the cooler and allowing steam to blow in for some time. 
If either of these methods is used, a by-pass around the brine pump 
must be supplied so as to drain the brine coil back to the tank without 



20 



STUDIES OF EECONSTRUCTED MILK. 



wasting the brine. These methods of sterihzation are very likely to 
cause leaks in the cooler, ov/ing to the uneven expansion of the coils. 
It was found at Nitro that satisfactory sterilization could be accom- 
plished by a thorough brushing with soda solution and then rinsing 
with approximately 200 gallons of water which had been previously 
heated to about 180° F. in one of the pasteurizing vats. From a 
bacteriological standpoint this method is not as efficient as draining 
the coils and appl3ang steam. 

m 
QUANTITY OF THE RECONSTRUCTED PRODUCTS MANUFACTURED. 

As has been stated, the plant had a capacity of at least 2,000 gallons 
of reconstructed products in an eight-hour day. This amount of 
milk was never sold in Nitro, owing to the impossibility of proper 
delivery. Nitro was never completely finished, and the streets, up 
to the cessation of operations, were in such poor condition that a 
house-to-house delivery could not be made. It was intended to sub- 
stitute for this retail delivery a wholesale delivery to a number of 
small distributing stations centrally located, where the various milk 
products could be purchased by the consumer and carried to the 
homes. This system would have had the advantage of elimJnating 
bottle loss. Unfortunately, these milk stations were not finished in 
time to take care of the rush. The fact that milk could be purchased 
only at the general stores cut the consumption greatly. 

Table I gives the daily quantities of the various products manu- 
factured during the months of September, October, November, and 
December, 1918, and part of January, 1919. 

Table I. — Quantity of reconstructed milk products manufactured daily at Nitro, W. Va,, 
during Sep te^nber, October, November, and December, 1918, and part of January, 1919. 



Date. 



Pounds 
of milk. 



Pounds 

of cream 

(2.5 per 

cent). 



Pounds 
of ice 
cream 
mix. 



Gallons 
of ice 
cream. 



1918. 
Sept. 6 


1,091 






9 


1,703 


10 


2,200 


11 


3, 000 


12 


3,500 


13 . 


3, 400 


14 


4,400 


15 


2,200 


16 


0,400 


17 


5,400 


18 . ... . 


4, 000 


19 


7,200 


20 . . 


4,800 


21 . 


2,400 


22 


4,400 


23 


4,800 


24 . . . . 


7, 200 


25 


4, 800 


26 


7, 200 


27 


7, 200 


28 


0, 3 ) ) 


29 


7, 2.M) 


30 


9, liOO 



























500 










s 




10 


1,000 


10 




10 


::::;.:::.! ;... 


10 
















10 


1,200 


25 



STUDIES OF KECONSTRUCTED MILK. 



21 



Table I. — Quantity of reconstructed milk products manufactured daily at Nitro, W. Va., 
during September, October, November, and December, 1918, and part of January , 1919 — 
Continued. 



Oct. 



Nov. 



Dec. 



11.. 
12.. 
13.. 
16.. 
17.. 
18. 
19.. 
20.. 
21.. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 



Date. 



1918. 



Pound.s 
of milk. 



7,20!) 



Pounds 

of cream 

(25 per 

cent). 



7,2;X) 
7,200 
7,200 
7, 200 
7,200 
7,200 
7,200 
7,200 
7,200 
7,200 
7,200 
7,210 
7,200 
7,200 
7,200 
8,400 
7,200 
7,200 
8,400 
8, 100 
8,400 
8,400 
9,600 
8,400 
8,400 
9,000 
9,600 
7,200 
8,400 
7,200 
7,200 
8,400 
8,400 
7,200 
8,400 
8,400 
7,200 
12,000 
9,600 
8,400 
7,200 
12,000 
4,800 
4,SO0 
7,200 
4,800 
4,800 
7, 200 
4,800 
4,800 
2,400 
4,800 
4,800 
4,800 
4,800 
4,800 
4,800 
2,400 
4,800 
2,400 
2,400 
4,8(X) 
2,400 
7, 200 
2, 400 
2,400 
4, 800 
4,800 
4,800 



2, 400 
2, 400 
2,400 
4,800 



500 



500 



Pounds 
of ioo 
cream 
mix. 



500 
500 



500 



500 



500 



500 



1,200 
1,210 



1,200 



1,200 



1,200 



Gallons 
of ice 
cream. 



1,200 



1,200 



600 



600 



1,200 



1,200 



1,200 



1,200 



1,200 



1,200 



1,200 



1,200 
1,200 



22 



STUDIES OF RECONSTRUCTED MILK. 



Table I. — Quantity of reconstructed milk products manufactured daily at Nitro, W. Va.y 
during September, October, November, and December, 1918, and part of January, 1919 — 
Continued. 



Date. 


Pounds 
of milk. 


Pounds 

of cream 

(2.5 per 

cent). 


Pounds 
of ice 

cream 
mix. 


Gallons 
of ice 
cream. 


Dec. 20 


1918. 


4,800 
2,400 
2,400 
2,400 
2,400 
2,400 
2,400 
2, 400 
2,400 

2,400 
2,400 
2,400 






60 


21 




45 


23 


500 




80 


24 


1,200 


00 


23 


. 


45 


27 . 


500 




50 


28 




45 


30 




1, 200 


55 


31 - 




30 


Jan. 1 . ... 


1919. 


1,000 




CO 


3 


600 


60 


4 


500 




5 




35 


6 


2,400 
2,400 
2,400 






30 


7 : 






45 


8 




1,200 


80 


9 




50 


10 


2,400 
4,800 


500 




45 


11 




40 


12 






65 


13 




500 


1,200 


80 


i; 


2,400 
2,400 


CO 


15 






85 


If) 


1 


40 






1 





The quantities of milk and cream produced are large enough to 
serve as a basis for economic considerations. 



OPERATING SCHEDULE. 

It was expected that full data on the cost of operation of this 
plant could be collected by keeping accurate labor charts and meter- 
ing the electric power, the water, and the steam consumed by each 
machine. Unfortunately the meters were lost in transit, due to 
congested traffic conditions, and this part of the data is not available. 
Time sheets of the various operations were kept, and the operating 
schedule given below was computed from them. 

The capacity of the plant depends on the time required to mix 
the ingredients and pasteurize them. It is therefore of first import- 
ance to determine the time required for the various operations con- 
nected with this part of the process. Accurate time sheets were 
kept for two months, and it was found that the following time inter- 
vals were required to perform the various operations included in the 
mixing, pasteurizing, and emulsifying of one batch, 282 gallons, of 
milk: 

Minutes. 

Weighing and transferring water and skimmed milk powder to vat 33 

Dissolving powder 10 

Emptjing skimmed milk vat IS 

Preparing and adding butter 13 

Heating mixture to 146° F 28 

Holding for pasteurization 30 

Emulsifying (2 emulsors in use) 45 



STUDIES OF RECONSTRUCTED MILK. 23 

Using these data, a daily schedule of operation of the three vats 
and two emulsors was planned. This schedule is given in Table II. 
Vats A and B represent the mixing and pasteurizing vats on the 
balcony, and vat S is the sldmmed milk vat located on the main 
floor. 

It will be noted from Table II that vat S is in continuous opera- 
tion, but that vats A and B are idle 20 minutes, and the emulsors 15 
minutes, between every two batches. This loss of time could be 
eliminated by changing the method of preparing the skimmed milk. 
Too much time is consumed in measuring and handling the water and 
powder. This time can be reduced by arranging the building so tha*^ 
the powder storage room and the distilled water storage tank are on 
the same level witli the present balcony. A weighed charge of pow- 
der could tlien be dumped directly into a hopper placed above the 
skimmed milk vat while the powder in the previous batch is dissolv- 
ing. If, at the same time, water from the elevated tank could be 
run directly into the mixing vat through a 4-inch conductor, the time 
of charging the vat could be reduced to approximately 10 minutes. 
An ordinary gauge glass attached to the end of the vat, extending the 
full height of the vat, could be calibrated accurately enough to pro- 
vide means of measuring the distilled water. By using this arrange- 
ment of measuring devices and by having the man responsible for 
the mixing of the skimmed milk commence work an hour ahead of 
the rest of the force, the output of the plant can be increased from 
six to eight batches per day. Such an arrangement is outlined in 
Table III. 

It will be noted that between Batches II and III, IV and V, and 
VI and VII there are 12-minute intervals during which no milk is 
passing through the emulsors. These delays are unavoidable when 
vats of this capacity are used. 



24 



STUDIES OF RECONSTEUCTED MILK. 



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STUDIES OF RECONSTRUCTED MILK. 



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utes, preparing i 
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Batch VI. 

utes, preparing 
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Batch VIII. 

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tes, emulsifying. 
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Batch III. 

es, preparing i 
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Batch V. 

es, preparing 
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minut 
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dissolving 
emptying 


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measuring 
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measuring 
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Batch VII. 


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26 STUDIES or RECONSTRUCTED MILK. 

OPERATING FORCE. 

A plant as described can be operated with a force of seven men. 
This force should consist of a foreman, who would have general 
charge of the plant and would personally operate the skimmed 
milk vat; an assistant foreman, who would spend his entire time on 
the balcony level, operating the pasteurizers and emulsors; three men 
operating the bottling and capping machine — one man feeding the 
machine with empties, one man removing the filled bottles, and one 
man handling the cases of empty and filled bottles — one man trucking 
the filled cans to the refrigerator, and one man operating the refriger- 
ating machine and assisting as his time permits at any temporary 
point of congestion. ' The foreman and assistant foreman should be 
men skilled in the handling of milk and the operation of milk machin- 
ery, and the engineer should, of course, understand the operation of 
a refrigerating machine. The other employees may be of a good 
grade of laborers. 

COST OF PRODUCING BOTTLED RECONSTRUCTED MILK. 

The cost of producing bottled reconstructed milk will vary with 
the locality and with the market price of the various commodities 
used in the manufacture and handling of the product; therefore, no 
exact figures can be given. It can be stated, however, that the cost 
of a plant to manufacture reconstructed milk, and the number of 
men and the amount of power necessary to operate it, are no greater 
than similar items in the operation of an ordinary modern pasteurizing 
and bottling plant, and therefore, the cost of manufacturing and 
bottling reconstructed milk is approximately the same as the plant 
charge for pasteurizing and bottling fluid milk. The delivery charge 
is, of course, identical in both cases. The economic advantage 
gained by drying the skimmed milk and manufacturing butter at the 
point of production and reconstructing the milk at the point of con- 
sumption, rather than handling it in the normal fluid state, lies in 
the difference in price between sweet fluid milk delivered in bulk at 
the pasteurizing and bottling plant, and powder, butter, and water 
delivered at the same location, plus the economic advantage gained 
by always having the supply equal the demand. 

Skimmed milk powder at the present time is manufactured in the 
great dairy regions of New York, Pennsylvania, Ohio, Indiana, Illi- 
nois, Michigan, Wisconsin, Minnesota, and on the west coast. Sweet 
butter is also manufactured in quantity in these States. Distilled 
water can be produced locally. The prices of powder and butter are 
necessarily the market prices at the point of manufacture, plus the 
freight charges. During the past year (1919) the market price of 
skimmed milk powder at the factories has varied in carload lots from 
20 cents to 26 cents per pound. Sweet butter has varied on the New 
York market from 46 cents to 71 cents per pound. Distilled water 



STUDIES OF RECONSTRUCTED MILK. 27 

can be made for less than one-quarter of a cent per gallon. Using 
these figures, the cost of the ingredients entering into a quart of milk 
containing 9 per cent solids not fat and 3.5 per cent fat will vary from 
7.9 cents to 13.3 cents. To this must be added the freight on the 
powder and butter, which is a minor item. The price paid the 
producers in the South, during this period, for normal fluid milk has 
varied from 10 cents to 20 cents per quart, depending on the locality. 
It is certain, therefore, that in these sections reconstructed milk can 
be sold for a lower price than normal milk. 

Whether reconstructed milk is more economical for a given com- 
munity than normal fluid milk can only be determined by a careful 
comparison of the prices of the raw commodities delivered at the 
point of consumption. 

If all the milk produced in the country could be dehydrated and 
subsequently reconstructed as needed to meet the demand, there is 
Uttle doubt that a great financial saving to the country at large 
would result. Until such method is universally adopted a careful 
study of the local conditions of each community must be made before 
deciding on the correct method of milk handling. 

From a bacterial standpoint reconstructed milk has decided advan- 
tages over market milk of good quality, as will be shown in the sec- 
tion on the bacteriology of this product. 

THE QUALITY OF THE FINAL PRODUCT. 

The manufacture of milk powder and reconstructed milk is in its 
infancy. The processes have been studied to some extent, but 
little is known regarding the effect of the various methods of drying 
and reconstructing on the composition of the finished product. 
Infant feeding experiments have been conducted in England, in 
which dried milk powder was used. These experiments are repoited 
in Food Reports No. 24 to the local government board on Public 
Health and Medical Subjects, New Series No. 116.^ These experi- 
ments indicate that children can be raised on reconstructed milk 
with no more difficult}^ than on normal cows' milk. 

To the casual adult drinker of milk, carefully produced recon- 
structed milk made from the better grade of powders available in 
quantity on the market to-day, has the appearance of normal milk, 
except that it lacks a cream line. It has a flavor slightly more 
''cooked" than the pasteurized market milk. This flavor to many 
observers gives the impression of excessive "richness." It is not 
objectionable to those used to pasteurized milk, but is somewhat 
distasteful to those accustomed to drinking raw milk. The freshly 
made product very easily passes for nrst-cl'iss noiuial milk. One 
sc:ious physical defect exists, however: the fat emulsion as produced 

'See also "Dried Milk Powder in Infant Feeding: Safety, Usefulness, and Comparative Value— A 
Preliminary Report," by W. H. Price, Surgeon (R.), United Slates Public Ileallh Service, Public Ilealtli 
Reports, vol. 35, No. 14, Apr. 2, 1920, pp. SU'J-ii2S.— Kuitoe. 



28 STUDIES OF EECONSTRUCTED MILK. 

at Nitro is not wholly permanent. On standing for 48 hours at a 
temperature approximately 35° F. or for 20 hours at room tempera- 
ture, a thin crust of butter forms on the top of the fluid. If the milk 
is kept in an ordinary refrigerator and consumed within 24 hours no 
separation is noticed. This '' buttering " in all probability is caused by 
some change in the complex ingredients of the skimmed milk brought 
about by the drying process. The power to hold fat in emulsion 
has been partially destroyed. As soon as this effect is overcome by 
the manufacturers, a product will be available which will readily 
compete with normal fluid milk. At present, reconstructed milk 
forms an excellent emergency supply which may readily take the 
place of normal milk during a shortage of the latter product. 

Summary. 

1 . Reconstructed milk and cream made from skimmed milk powder, 
unsalted butter, and water have been produced in large quantities 
at Nitro, W. Va., and sold to the public. 

2. The cost of manufacturing these products in the Southern 
States is less than the cost of local normal milk. As the distance 
between the points of efficient production and consumption is less- 
ened, this diflFerence in cost becomes less. In the dairy sections at 
the present time fluid milk can be sold more cheaply than recon- 
structed milk. 

3. Reconstructed milk products serve as excellent emergency 

supplies, and as soon as the process of manufacturing milk powder 

is perfected they wiU no doubt compete in the open market with 

normal milk products. 

Acknowledgments. 

The authors wish to express their appreciation of the valuable 
assistance given them throughout this demonstration by Passed 
Asst. Sm-g. J. A. Watkins, of the United States Public Health Service, 
resident officer in charge of the department of medical relief and 
sanitation of Nitro; Mr. Hugh C. Leighton, executive officer of the 
Nitro commissary department; Mr. C. S. Bassett; Mr. L. C. Johnson; 
Mr. R. G. Soule; and all others who through suggestions or material 
aid helped in making the demonstration a success. 

II. AN ANALYTICAL STUDY OF RECONSTRUCTED MILK. 

By Albert F. Stevenson, Sanitary Engineer, and C. P. Rhyntjs, Assistant Sanitary Engineer, United 

States Public Health Service. 

Before any process devised for the handling of milk can be pro- 
nounced a success, an analytical study of the product, both from a 
bacteriological and chemical standpoint, must be made. If this 
study shows the product to be materially altered or to be a potential 
source of danger, from a health standpoint, the process is valueless. 

It was therefore of the greatest importance to determine in this 
plant, the initial one producing reconstructed milk on a commercial 



STUDIES OF RECONSTRUCTED MILK. 29 

scale, whether the product was of a high or low grade, from a 
bacterial and chemical standpoint. 

A plant laboratory was installed where bacteriological analyses 
could be made. It was possible by this means to check the plant 
operation and to determine, at all times, the quality of the product 
which was being sold. As is always the case, the field laboratory 
proved one of the most important assets of the plant. Samples of the 
finished product as well as samples from the various stages of the 
process of manufacture were analyzed daily. The finished product 
was again sampled and analyzed, after delivery, by the division of 
health and sanitation of the Nitro organization. These last analyses 
correspond to those which would be made by the board of health of 
an ordinary community. 

The methods employed in making bacteriological analyses were 
those recommended by the committee on standard methods of milk 
analysis of the American Public Health Association. Samples were 
collected from the various stages of the process of manufacture, in glass 
test tubes plugged with nonabsorbent cotton. Filled pint bottles, 
selected at different periods during the day, served as bottled milk 
samples. These samples were refrigerated until the actual analysis 
was made, which occurred, generally, within two hours of the time of 
sampling. The culture media used for the bacteriological analysis 
were made at the Hygienic Laboratory in Washington, D. C, and 
shipped to Nitro in tin containers. The media were transferred from 
the cans to 4-ounce glass bottles, after arriving at the plant, and were 
then resterilized. A check titration was always made on each ship- 
ment of media, after the final sterilization in the glass bottles. Sterili- 
zation of media was accomplished by heating for one hour at 100° C. 
in an Arnold sterilizer for three consecutive days, and then incubating 
the media for 24 hours to throw out any contaminated bottles. The 
dilution water was sterilized in the same manner. Dry sterilization 
was accomplished in the oven of an ordinary gas stove. Forty-eight- 
hour 37° C. total counts were made on the various samples. No 
attempt was made to isolate any particular organism. 

The results of the bacteriological determinations made on the 
finished reconstructed milk in the final containers are given in 
Table IV. Table V shows the results of arranging these counts in 
the order of magnitude. Seventy-five per cent of them were 5,000 
or less. The highest count obtained was 55,000, and only three 
times was a count over 30,000 obtained. 

Total comits made on the bottled milk by the department of 
sanitation are given in Table VI. Rearrangement of these comits in 
the order of magnitude, as shown in Table VII, em})hasizes the fact 
that 15 per cent of them are imder 1,000 and 97 per cent are under 
5,000. Only one count out of the total 33 was greater than 5,000. 



30 



STUDIES OF KECOlSrSTEUCTED MILK. 



A bacteriological study of the manufacturing process brought out 
some useful information. Table VIII gives the number of bacteria pres- 
ent in reconstructed skimmed milk. These figures, of course, include 
both the number of bacteria in the water and in the milk powder. 

Table IV. — Bacterial content of finished product in container. 





Bac- 




Bac- 




Bac- 




Bac- 




Bac- 


Date. 


teria 


Date. 


teria 


Date. 


teria 


Date. 


teria. 


Date. 


teria 




per c.c. 




per c.c. 




per c.c. 




per c. c. 




per c.c. 


1918. 




1918. 




1918. 




1918. 




1919. 




Sept. 15 


7,000 


Nov 4 


1,200 


Nov. 25 


1,300 


Dec. 13 


2,900 


Jan. 7 


1,200 


16 


8,000 


5 


6, 900 


26 


1,400 




2,100 


8 


1,500 




6,000 




7,000 




200 




800 




700 


18 


7,700 




6,200 




1,300 




7,700 


10 


3, 400 


19 


10, 000 




3,500 




500 


14 


2,000 




650 


20 


1 , 400 


6 


13, 500 




200 


16 


3,600 




23, 000 




5, 100 




3,700 


27 


2, 500 




28, 000 


11 


20, 000 




2,200 




15, 800 




200 




6,000 




21,000 


21 


3,400 


7 


5,000 


28 


800 


17 


3,300 




21,000 


23 


1,200 




2, 000 




200 


18 


3.500 




9,600 




300 




2,500 




200 




600 




4, 600 




100 




3,100 




200 




700 




5, 500 


24 


1,000 


11 


15, 500 


29 


1,500 


19 


2,600 


14 


6,900 


25 


1,200 


12 


1,600 




700 




1 , COO 




1,500 


26 


2,700 




3, 200 


30 


4,000 


20 


2,200 




1,800 


30 


11,000 




8, 000 




2,700 




2,300 


15 


17, 500 




2,400 




1,600 




3, 800 


21 


19,000 




3,000 




1,100 




1,600 


Dec. 1 


2 , 100 


23 


15, 600 




4,500 


Oct. 1 


3, 000 




3, 000 




1,700 




4, 100 


17 


9,400 


10 


13, 000 


13 


1,400 




500 




4,700 




1 1 , 000 




400 




3, 000 


2 


4,600 


24 


8,600 




12,000 


11 


13, 500 




2,800 




500 




2,800 


18 


19, 000 


12 


7,000 


16 


4,700 


3 


15, 000 


26 


10,000 




IS, 000 


14 


30, 100 




6,200 




2,000 




2,200 




55,000 


16 


1,200 




2,700 




2,000 




700 


21 


1,600 


17 


3, 100 




2,100 




1,000 


27 


4, 000 




200 




1,300 




1 , 600 




1,000 




2,000 


22 


1,700 


21 


6,000 


17 


20, 000 




600 




500 




400 




4,400 




1,100 


4 


300 


28 


26, 000 




11,000 


22 


1,200 


18 


4,500 


5 


2,000 




1,800 


23 


4,000 




5,900 




2,200 




1,300 




900 




1,700 




2, 100 


19 


2,400 


6 


1,600 


30 


4,400 




1,300 


23 


13, 000 




1,100 




1 , 000 




2,000 


26 


5, 700 




22,000 




600 


7 


3,100 




5,500 




1,500 


24 


1,400 




2,400 




1,500 


31 


4, 700 




3, 100 




2,100 




200 




5, 000 




1,200 


27 


300 


28 


3, 300 


20 


2,700 


9 


1,500 




600 




1,400 




2,800 




1,700 




1,!-00 




600 




800 


29 


12,000 


21 


600 




1,200 


1919. 




28 


12,000 




6,800 




600 


10 


4,300 


Jan. 2 


3,600 




700 


30 


3,000 




2,300 




1,200 




1,300 




1,000 




500 




2,800 




800 




26, 000 


30 


1,300 


31 


2,000 


22 


1,100 


11 


3,700 


3 


1,600 




1,000 




600 




250 




3, 100 




1,900 




700 


Nov. 2 


2,000 




600 




1,000 


4 


2,000 




1,000 


3 


1,000 




6, 000 


12 


5, 000 




3,000 


31 


2,800 


4 


30, 000 


24 


1,600 




2,900 


6 


2,300 




1,000 




3,500 




12,000 




1,800 




3, 200 




800 




1,000 


25 


1,900 




2,800 




500 




1,300 




1,700 




1,300 


13 


1,200 


7 


2, 100 







Table V. 



-Results of arranging bacteriological counts of bottled milk according lo 
magnitude. 



Range of counts. 



Number 

of counts 

within 

range. 



Percent 

of counts 

witiiin 

range. 



Range of counts. 



Number 

ofcounts 

within 

range. 



Per cent 

ofcounts 

witliin 

range. 



Under 1,000. 
1,000-2,500.. 
2,500-5,000.. 
6,000-7,500.. 
7,500-10,000. 
10,000-15,000 
15,000-20,000 



17.4 
36.6 
21.8 
8.1 
2.8 
5.3 
3.2 



20,000-25,000 
25,000-30,000 
30,000^0,000 
40,000-50,000 
Over 50,000. 

Total. 



STUDIES OF RECONSTRUCTED MILK. 



31 



Table VI. — Bacteriological examinations of reconstructed milk made by the Sanitary 

Division, Nitro, W. Va. 



Date. 


Source. 


Bacteria 
per c. c. 


Date. 


Source. 


Bacteria 
perc.c. 


1918. 
Sept. 23 


McssHallNo. 2 


2,000 
1,650 
2,350 
2, 150 
2,000 
1,950 
8, 600 
1,950 
2,600 
2,900 
2,700 
2, 850 

900 
2, 500 
1,.500 
1,400 

700 
1,800 


1918. 
Dec. 16 
17 
19 
20 
21 

2:^ 

24 
26 
27 
28 
31 

1919. 

Jan. 1 

2 

3 

4 


Hospital mess No 2 


200 


24 


Hospital mess 


do 


5S0 


25 


do 


do 


1 550 


26 


do 


do . 




27 


do 


do 


1 900 


28 


do 


do 


2 1.50 


30 


do 


do . 




Oct. 1 


do 


do 


2 100 


2 


do 


.. ..do 


2,450 
2,000 
2 800 


3 


do 


do 


4 


do 


do 


5 


do 


do 




Nov. 11 


do 




12 


do 


7.50 


13 


do 


do 


1 1.50 


14 


do 


.. ..do ^ . 


1 550 


15 


do 


do . . 


1 200 


16 


do 













Table VII.- 



-ResuUs of rearranging the bacteriological analyses made on the bottled milk 
by the Sanitary Division, Nitro, W. Va. 



Range ofcounts. 


Number 

ofcounts 

within 

range. 


Per cent 

ofcounts 

within 

range. 


Underl.OOO 


5 

27 

1 


15 


1,000-5,000 


82 


Over5,000 - - -. 


3 




_._ 




Total 


33 


100 







Table VIII. — Bacterial content of reconstructed skimmed milk. 



Date. 


Bacteria 
per cc. 


Date. 


Bacteria 
percc. 


1918. 
Oct. 14 


17,400 

61,000 

113, (KK) 

27, 600 

4,200 

7,S00 

5,700 

5,300 

15,000 

6, 700 

9,000 

24,400 

41,200 

61,010 

43, .^00 

27, 400 

39,000 

22,000 


1918. 
Dec. 14 


58 000 


16 


16 


246,000 


17 


19 


40 000 


22 


26 


12,100 


30 


27 


23 000 


Nov. 4 


30 


32 000 


12 


31 


8,000 


19 


1919. 
Jan. 2 


22 




25 


50,000 


26 


3 


51,000 


29 


4 


15,300 


30 


11 


4,000 


Dec. 1 


15 


126,000 
40,000 


3 


17 


9 . 


IS 


280,000 


12 


23 


12,000 


13 


30 


22,000 









Rearrangement of these figures, as in Table IX, shows that 23.4 
per cent of the counts are below 10,000, and 76.4 per cent are below 
50,000. 



82 



STUDIES OF KECONSTRUGTED MILK. 



Table IX. — Result of arranging the bacterial counts of samples of reconstructed shimmed 
milk according to magnitude. 



Range of values. 



Number 

of counts 

within 

range. 



Under 10,000. 
10,000-50,000. 
50,000-100,000 
Over 100,000. 

Total.. 



Per cent 

of counts 

within 

range. 



8 


23.4 


18 


53.0 


4 


11. S 


4 


11.8 



100.0 



Table X gives the bacterial content of the butter used. A weighed 
amount of butter was added to sterile dilution water and the mixture 
warmed until the butter melted. This mixture was then shaken 
vigorously and the water layer analyzed. The results obtained are 
somewhat lower than might be expected. 

Table X. — Bacterial content of butter. 



Date. 


Bacteria 




per c.c. 


1918. 




Oct. 22 


38,000 


Nov. 4 


13,000 


22 


2,000,000 


30 


250,000 


Dec. 3 


280, 000 


1919. 




Jan. 4 


120,000 


17 


650,000 


30 


35,000 



Counts were also made from the milk as it passes from the mixing 
and pasteurizing vats to the emulsors. These are shown in Table XI. 

Table XI. — Skimmed milk and butter mixture after pasteurization. 



Date. 


Bacteria 
per c. c. 


Date. 


Bacteria 
per c.c. 


Date. 


Bacteria 
per c.c. 


Date. 


Bacteria 
per c.c. 


Date. 


Bacteria 
per c. c. 


1918 




1918 




1918 




1919 




1919 




Oct. 16 


1,600 


Nov. 30 


400 


Dec. 13 


520 


Jan. 2 


3,560 


Jan. 22 


30,000 


17 


500 


Dec. 2 


760 


14 


660 


2 


720 


22 


300 


22 


1,000 


3 


4,100 


16 


800 


3 


1, 150 


23 


600 


30 


500 


3 


1,100 


16 


440 


4 


910 


23 


890 


31 


700 


3 


1,400 


18 


1,200 


6 


3,000 


26 


600 


Nov. 4 


3,100 


4 


1,100 


18 


200 


7 


3,200 


26 


780 


12 


2,600 


4 


180 


19 


910 


8 


600 


27 


500 


12 


4,400 


7 


5,100 


21 


6,500 


10 


2,600 


27 


1,100 


19 


100 


7 


600 


23 


6,000 


11 


12,600 


28 


1,800 


22 


150 


9 


370 


26 


100 


11 


7,100 


28 


910 


22 


70 


10 


24,600 


26 


580 


14 


7,900 


30 


1,400 


25 


830 


10 


800 


27 


100 


14 


1,400 


30 


740 


25 


340 


11 


14, 000 


27 


930 


15 


21,200 


31 


450 


26 


310 


11 


600 


28 


1,750 


15 


1,600 






26 


210 


12 


3,500 


28 


305 


17 


11,000 






28 


170 


12 


950 


30 


820 


17 


9,400 






29 


400 


12 


1,900 


31 


200 


18 


40,000 






30 


1,700 


13 


2,400 


31 


580 


18 


9,300 







STUDIES OF RECONSTRUCTED MILK. 



33 



The killing of the bacteria in the butter and skimmed milk mix- 
ture depends, of course, on the length of time this mixture is heated. 
Samples taken at the first stages of a run or immediately after the 
30-minute holding period, showed counts slightly higher than sam- 
ples taken at the end of the emulsification period. This was due, of 
course, to the fact that the last of the mixture to flow from the 
mixing vats into the emulsors had approximately 45 minutes more 
heating at 146° F. than did the first of the batch. Typical results 
showing the variation in bacteria at the beginning and end of a 
batch are given in Table XII. 

Table XII. — Difference in bacterial count at beginning and end of batch from emulsors. 





Bacteria per c.c. 


Date. 












Begin- 


End. 




ning. 




1918. 






Dec. 1 


1,400 


4.-,0 


3 


2,600 


420 


11 


7,200 


720 


12 


6,000 


710 


16 


1,300 


450 


26 


1,200 


780 


1919. 






Jan. 2 


1,100 


920 


11 


15,000 


3,700 



Analyses were also made of the discharge from the emulsors and 
from the cooler. These figures show little if any variation from the 
corresponding counts on the milk coming directly from the mixing 
vats, and are not given. 

Bacteriology of Cream. 

Bacteriological counts were also made on the reconstructed cream 

which was produced at Nitro. A summary of these results is given 

in Table XIII. These figures, rearranged in the order of their 

magnitude (Table XIV) show that 74.2 per cent of the counts were 

below 10,000. 

Table XIII. — Bacterial content of cream. 



Date. 


Bacteria 
per c.c. 


Date. 


Bacteria 
per c. c. 


1918. 
Nov. 4 


2,200 
7,000 
4,000 


1918. 
Dec. 13 


7,700 


12 


13 


3,400 


18 


17 


3,100 


18 


4,. "00 


23 


6,600 


21 


1,500 

9,600 

400 

24,200 

25,000 

4,300 

2,000 

12,000 

6,000 

5,900 

5,100 

25,000 

72,000 


27 


4,500 


23 


27 


38,000 


24 


1919. 
Jan. 2 




25 




30 


5,300 


Dec. 2 


4 


6,000 


2 


10 


6,200 


3 


13 


5,100 


7 


20 


27,000 


7 


24 


50,000 


7 


25 


3,200 


10 


29 


2,100 


12 











34 



STUDIES OF RECONSTRUCTED MILK. 



Table XIV. — Results of arrangement of bacterial counts on reconstructed cream in 

order of magnitude 



Range of values. 



Under 5,000. 
5,000-10,000.. 
10,000-30,000. 
30,000-50,000, 
Over 50,000.. 

Total. 



Nirmber 

of counts 

falling 

within 



Per cent 
of counts 
falling 
within 
range. 



12 


38.7 


11 


35.5 


5 


16.1 


2 


6.5 


1 


3.2 



100.0 



Bacterial Content of Ice- Cream Mix and Ice Cream. 

There has been a decided controversy recently concerning the 
bacterial content of well-made ice cream, and many have taken the 
stand that it is impossible to produce good ice cream with a low 
bacterial count. At Nitro, ice cream was manufactured in a rather 
cnide manner, one which would tend to give the product a much 
higher bacterial content than that produced with modern up-to-date 
machinery. The bacterial content of the ice-cream produced at 
Nitro was, therefore, determined with many misgivings, for it was 
thought that the figures might be misleading. Samples were taken 
of the mix shortly after it was manufactured and before any storage 
period had elapsed. Between the manufacture of the mix and the 
manufacture of the finished ice cream the mix was allowed to stand 
at a temperature of approximately 33° F. for 24 hours. On manu- 
facturing, the mix gave 95-100 per cent "swell," showing that it 
was sufficiently aged to be commercially useful. Table XV gives 
the bacterial content of the ice-cream mix, and Table XVI that 
of the finished ice cream: 

Table XV. — Bacterial content of ice-cream mix. 



Date. 


Bacteria 
per c. e. 


Date. 


Bacteria 
per c. c. 


Date. 


Bacteria 
per c. c. 


1918. 




1918. 




1918. 




Oct. 12 


1,700 


Dec. 3 


2,200 


Dec. 30 


4,600 


Nov. 5 


7,200 


3 


11,400 






11 


2,100 


7 


1.5,000 


1019. 




16 


4,000 


9 


3,400 


Jan. 3 


5,000 


18 


1,300 


10 


4,600 


8 


5,100 


20 


2,200 


12 


6,400 


13 


6,700 


21 


800 


14 


15,400 


17 


31,000 


26 


2,100 


18 


1,300 


20 


5,000 


26 


7,000 


21 


1 , 700 


21 


4,000 


30 


2, SOO 


24 


6, 500 


24 


6,000 


30 


1,600 


24 


22,000 


29 


70, 000 


Dec. 2 


300 


28 


1,650 


30 


1,200 



STUDIES OF RECONSTRUCTED MILK. 
Table XVI. — Bacterial content of ice cream. 



35 



Date. 


Bacteria 


Date. 


Bacteria 


Date 


Bacteria 




per c. c. 




perc.c. 




perc.c. 


1918. 




1918. 




1919. 




Nov. 18 


30,200 


Dec. 10 


37,000 


Jan. 20 


84,000 


21 


2,000 


12 


7, 000 


21 


9,000 


26 


10,5, 000 


18 


18,,SOO 






30 


23,000 


21 


27, 200 






Dec. 2 


16, 000 


24 


3,000 






7 


4,500 


28 


1,800 







Rearrangement of these figures shows that 79.5 per cent of the 
counts on the ice-cream mix were below 10,000, and 71.5 per cent 
of the counts on the finished ice cream were below 30,000. These 
figures indicate that, under average conditions, an ice cream can be 
manufactured with a bacterial content which approximates that of 
well-pasteurized creams. 

Butter-Fat Content of Reconstructed Milk. 

In the operation of a plant manufacturing reconstructed milk, one 
of the important features is the proper mixing of the ingredients so 
that the percentage composition of the various constituents are as 
stated on the final package. The butter used in the making of the 
products at Nitro was bought with the moisture content guaranteed 
to be not over 15 per cent. Enough samples of this butter were 
analyzed to show that the specifications were being complied with, 
but no detailed analyses were made on the various tubs of butter 
used from day to day. It was assumed always that the butter con- 
tained at least 85 per cent fat. Butter-fat determinations made on 
the finished product brought out the fact that the butter purchased 
in many cases had a moisture content much less than 15 per cent, 
making the fat content of the milk greater than was guaranteed. 
This fact points out the great need for butter analysis, both by the 
manufacturer and by the purchaser. The moisture content of a 
sample from every churning, at least, should be determined, and if 
possible this figure should be stamped on the tubs shipped. In all 
cases a sufficient amount of butter was added to the milk mix to 
give 3^ per cent fat, assuming the butter contained 85 per cent 
butter fat. 

Analyses of bottled milk were taken a>t first which showed that 
some variation existed in the fat content of the various containers 
as put on the market, A study was made to determine whether the 
fat content of the reconstructed milk at different points in the emul- 
sification of a single batch varied. The results of these analyses are 
compiled in Table XVII. Those values which are grouped around 
definite points have been averaged, giving the values shown in 



36 



STUDIES OF RECONSTRUCTED MILK. 



Table XVIII. These values have been plotted in Figure 8. It is 
easily seen that the fat content at the start is generally less than 
3^ per cent, whereas at the end of the run it is much less than 3^ 
per cent. After 70 per cent of the batch has been run through the 
emulso]-, there is a decided failing off in the percentage of butfter fat 



4.0 

3.5 

3.0 
k 
b2.5 

2.0 

1.5 


2 OF Batch Discharged Previous to Samplimg. q 

" 20 40 60 so 2 








































































































































^ 


*^ 




















rf' 


^ 


«^ 


W*" 


























s 














A 


^ 


r^ 


































s 










y 


y 








































v 






















■ 




























\ 


\ 


















































\ 




















































^ 


















































> 




















































L 


















































\ 


















































> 



























































































































































































































































































































































































































































































































































































































Fig. 8.— Variation in butter-fat content of reconstructed milk at various points in tlie manufacture of a 

single batch. Nitre, W. Va. 

in the product. As the vat agitator is in continual motion during 
the whole process of the emulsion, the reason for the very consistent 
variation in fat content is not obvious. However, as the condition 
exists, a cold milk storage vat should be supplied with every installa- 
tion to allow the equalization of the fat content before bottling. 



STUDIES OF RECONSTRUCTED MILK. 



37 



Table XVII. — Results of butter determinations made at various points during the 
emulsification of a batch of reconstructed milk. 



Date. 


Per cent of run discharged previous to sampling. 





3 


12 


13 


14 


16 


25 


27 


28 


29 


38 


40 


42 


43 


50 


53 


1918. 
Dec. 11 


3.5 
3.4 
3.4 

3.4 
3.1 
3.5 




























3.C. 
3.6 




14 




3.5 








3.7 








3.7 










14 




3.7 






3.8 








3.8 




1919 
Feb. 8 


3.4 




3.6 


3.7 




i'o' 

3.8 


3.6 




3.8 


3.6 







10 


3.8 


11 




















3.8 





























Date. 


Per cent of run discharged previous to sampling. 


55 


57 


62 


67 


68 


72 


75 


80 


81 


83 


86 


87 


88 


93 


94 


97 


100 


1918. 
Dec. 11. ... 














3.7 
3.6 






3.3 














2.7 


14 






3.6 
















3.3 








2.8 


14.. 




3.9 






3.9 








3.5 










3.2 


1919. 
Feb. 8 . .. 


3.5 




3.8 


3.7 






3.6 










3.0 


2.8 


2.3 


10 






3.7 
3.7 






3.5 
3.7 




3.2 
3.3 


3.0 


11 








3.8 


















2.0 





























Table XVIII. — Average values of butter-fat determinations made at various points 
during the emulsification of a batch of reconstructed milk. 



Per cent of 




run dis- 
charged 


Per cent 
butter fat. 






sampling. 







3.4 


14 


3.6 


27 


3.7 


41 


3.7 


54 


3.7 


66 


3.7 


74 


3.7 


84 


3.5 


95 


3.0 


100 


2.7 



Summary. 

1. Studies of the bacterial content of this plant's output of recon- 
structed milk and cream show that it was satisfactory from a health 
standpoint. 

2. It has been demonstrated that satisfactory ice cream can be 
manufactured on a commercial scale, with a bacterial content com- 
parable to that of well-pasteurized milk and cream. 

3. Using the revolving coil type of ice-cream batch mixer for mix- 
ing the ingredients entering into reconstructed milk, a product of homo- 
geneous fat content can not be made, and the final product from an 
entire batch should be mixed before bottling. 



o 



